Color stabilization of refined maleic acid anhydride

ABSTRACT

Refined maleic anhydride is provided with improved color stability by the addition of a treating agent comprising organic compounds containing a labile halogen.

United States Patent Stenseth et al.

Sept. 2, 1975 COLOR STABILIZATION OF REFINED MALEIC ACID ANHYDRIDE Inventors: Raymond E. Stenseth, St. Louis;

Ronald J. Boyer, Festus. both of Mo.; Richard J. Sheehan. Palos Hills, ll].

Assignee: Monsanto Company, St. Louis, Mo.

Filed: July 31, 1972 Appl. No.: 276,549

Related U.S. Application Data Continuationin-part of Ser. No. 41.116. May 27. 1970, abandoned.

US. Cl. 260/346.8 Int. Cl. C07D 307/60 Field of Search 260/3468 M References Cited UNITED STATES PATENTS 6/l97l Martinez ct a! 260/3468 Primary Eraminer-Henry R. Jiles Assistant E.\'aminerBernard I. Dentz Attorney, Agent; or Firm-N. E. Willis; J. E. Maurer; F. D. Shearin [57] ABSTRACT Refined maleic anhydride is provided with improved color stability by the addition of a treating agent comprising organic compounds containing a labile halogen.

l0 Claims, No Drawings '1 COLOR STABILIZATION OF REFINED MAL EIC ACID ANHYDRIDE CROSS-REFERENC ES TO RELATED APPLICATIONS This application is a continuation-impart of application Ser. No. 41,116 filed May 27, 1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the color stabilization of refined dicarboxylic acid anhydrides. More particularly, it relates to the color stabilization of refined maleic anhydride.

Anhydrides of certaindicarboxylic acids are commercially available to the consumer in either solid or molten form. Although these anhydrides are classified as chemically stable compounds, some discoloration of the solid material may be detected after extended storage periods. This rate of discoloration is more pronounced particularly when the anhydrides are maintained in their molten state for extended periods at elevated temperatures.

Maleic anhydride, for example, is often shipped in molten form in heated, insulated tank cars and is thus maintained in this state for long periods of time. Under such conditions, the molten maleic anhydride will frequently darken and become discolored.

Maleic anhydride can be prepared by the vaporphase oxidation or organic compounds such as benzene, toluene, naphthalene, methyl naphthalene, phenol, cresol, benzophenone, furan, biphenyl, furfural, n-butane, lbutene, Z-butene, butadiene, heptane, isooctane, crotonaldehyde and crotonic acid, employing a large excess of air. By-products of the above reaction include other organic acids, chromogenic bodies, carbon monoxide, carbon dioxide and water. Crude maleic anhydride is generally dark in color, and although crude maleic 'a nhydride can be refined to a substantially colorfree material, color reappears over a period of time as hereinable described. Color is an undesirable characteristic of maleic anhydride and, if present before or during processing, can cause deleterious effects in resulting products, such as plastics, where proper color is an important feature of the material.

The prior art discloses various methods for refining crude maleic anhydride to obtain a high grade product of low color. One such method is disclosed in US. Pat. No. 2,296,218 to Middleton, wherein crude maleic anhydride containing volatile color imparting compounds produced as by-products in the partial oxidation of organic compounds is treated in the liquid state with a modification agent selected from the group consisting of the oxides and hydroxides of sodium, potassium, lithium, calcium, zinc and magnesium, and the halides of zinc, iron and aluminum and reaction products thereof. Thereafter, the treated maleic anhydride is subjected to distillation, leaving the darkening impurities in the distillation residue.

The prior art also discloses various methods for improving the storage color stability of dicarboxylic acid anhydrides. One such method is disclosed in US. Pat. No. 3,1 15,503 wherein color stabilizing amounts of ethylenediaminetetracetic acid are added to a molten cyclic anhydride during the preparation process or thereafter. Alternatively, the acid is added to the finely divided solid cyclic anhydride prior to compressing into tablets or briquettes.

Another method is taught in US. Pat. No. 3,586,703 wherein smallamounts of a color stabilizer are incorporated into refined maleic anhydride. The stabilizers were such various inorganic compounds as hydrochloric acid, hydrobromic acid, silver chloride, barium nitrate, alkali or alkali metal sulfates, chlorides or bromides.

SUMMARY OF THE INVENTION Despite thev known prior art efforts to improve the color stability of maleic anhydride, there remains a need for further improvement. It is an object of the present invention, therefore, to provide color stabilized maleic anhyride. Another object of the present invention is to provide a color stabilizing amount of a treating agent. Still another object of the present invention is to significantly retard discoloration of solid and mo]- ten refined maleic anhydride during storage. Yet another object of the present invention is to provide a process for color stabilization of refined maleic anhydride by the introduction of novel treating agents.

These and other objects are achieved by introducing into refined maleic anhydride a color stabilizing amount of a treating agent to form a composition comprising a major amount of refined maleic anhydride and a color stabilizing amount of an organic compound containing a labile halogen.

For the purposes of this invention the term labile halogen" is defined as a halogen which is prone to undergo ionization or dissociation. Such a compound gives a positive result with the classical silver nitrate test. The term refined maleic anhydride. refers to that maleic anhydridehaving very little or no color that is suitable for use in commerce without further purification steps.

Color stabilized compositions obtained through use of the treating agents of this invention exhibit superior color properties as will be demonstrated by test results hereinafter presented.

It has been discovered that organic compounds containing 21 labile halogen, i.e., organically bound labile fluorides, chlorides, bromides and iodides, are superior treating agents for the color stabilization of refined maleic anhydride. Although not to be construed in a limitating sense, the following organic compounds containing a labile halogen can be used to color stabilize refined maleic anhydride: benzal chloride; benzyl chloride, benzotrichloride; orthoand paranitrochlorobenzene; orthoand para-toluenesulfonyl chloride; allyl chloride; methanesulfonyl chloride; so-

dium p-toluenesulfonchloramide; N- chlorosuccinimide; chlorosulfonic acid; 8- quinolinesulfonyl chloride; and meso-oz,a

dichlorosuccinic acid.

The acid halides of aliphatic and aromatic carboxylic acids are also useful. Examples of such carboxylic acid halides include acetyl chloride; adipoyl chloride, anisoyl chloride, acryloyl chloride, butyryl chloride, camphoroyl chloride, caproyl chloride, cinnamoyl chloride, cyanoacetyl chloride, formyl chloride, fumaroyl chlo ride, glutaryl chloride, isophthaloyl chloride, levulinoyl chloride, lauroyl chloride, malonyl chloride, oleoyl chloride, oxalyl chloride, propinonyl chloride, pyruvoyl chloride, salicyloyl chloride, stearoyl chloride, suberoyl chloride, terephthaloyl chloride, thioacetyl chloride,

and toluoyl chloride. It has been found that acryloyl chloride, benzoyl chloride. fumaroyl chloride; and phthaloyl chloride are quite effective.

It has been discovered that organic compounds con- 4 DESCRIETION OF PREFERRED EMBODIMENTS The following examples illustrate the advantageous and unexpected results that are achieved through the use of the treating agents of this invention. These exam- P a -l halogen Q beneficial treat 5 ples are intended to be illustrative only and are not to ing-agents for the color StublllZzltlOtT of maleic anhybe construed limiting Sense dride. Examples of organic compounds containing a v I non-labile halogen, and thus outside the present invei EXAMPLES 1 THROUGH are chlfarobenzerle and Carbon tetracmoffde' 10 Examples 2 through l5 demonstrate the effectiveness anhydncle can be Color stablh7' ed by of a variety of halogen-containing treating agents in imtreatment the treatmg agents of h present mven proving the heat stability of refined maleic anhydride. accordmg to mfmemus Q Successflfl The first example is given to show the color that develsults have been achieved by adding the color stabil zer Ops in untreated maleic anhydride l to molten f P f m P l 5 Untreated samples from various lots of commercially line at the-manufacturing site. It is somet mes desirable pure maleic anhydride were melted in a 25 by 200 to treat refined molten maleic anhydride in the melting test tube and the initial of colors were kettle or in a heated tankcar. In general, the means of termined at Sample temperatures from about to flddmg l agent Q f h treat about 70C. by comparison with the APHA color stanerem are usul y so u e m t e em army dards. The standard used to indicate the quantity or inn h tensity of color of products in solution form is known smce ogamcomhmmg treatfng of the as the APHA standard color test. This-test is one develg ffi h a i be s fi g 2 s i a oped by the American Public Health Association and e refne t 0 0 Intro uccmg e is known as the Hazen Platinum Cobalt Scale, a detreating agent 18 much simpler in contrast to many prior scription of which is found in volume 2', part 13, on an mcthods wher'cm a CQOkmg agertlt must be adfjed to page 2425 of the 6th edition of Standard Methods of the crude anhydride during processing. Those prior art Chemical Analysis," by R l Welcher, editor methods of introducing color stabilizer during pro- Temperatures of the untreated samples were then cess mg generd ny si m the pohmerzaton or l raised to l40C. and color values were determined j ,lmpurmes mak,mg P e after 2 hours, 4 hours, 6 hours and 24 hours of heating. by dlstmatlon The h f dlstmgwshed The color values for the untreated maleic anhydride therefrom in that no distillation or other processing Samples from a number of tests were averaged and are steps after treatment is necessary in the method depresented as Example 1 in Table I below where the scnbd r treating agent is indicated as None. After 4 hours at mp y Small amounts Ohthe hg agents 140C., the average APHA color of all untreated samof the present invention are effective to inhibit color pieswas 500 Th average initial or color was formation in refined maleic anhydride. It is to be recog- 15 hized that there is some Variation in Properties among Likewise, additionalsamples of the aforementioned different lots and sources of maleic anhydride. F urtherl i h d i were melted and treated with various more, some lots of maleic anhydride are more difficult 4o halogen-containing treating agents within the scope of o' treat h n Others- A ingly, there W111 be some the present invention. APHA color determinations for variation in the optimum amount of treating agent in ea h f th t t d am le were made in the manner the treated product depending up n th p o and described above. These APHA color determinations the treating agent selected. Thus, the concentration of are presented in Table I below. Except as noted, the the treating agent Whhih the treated P y y halogencontaining treating agent was added to the molfrOm a trace amount. as for CXflmPle P P ten maleic anhydride at a concentration of parts per lion y g to 1 0 parts per million by weight of million. Where the phrase parts per million is used greater. Generally, from 0.01 to 100 parts per million herein, the parts are parts by weight based upon the by weight is sufficient. weight of the dicarboxylic acid anhydride.

TABLE I APHA APHA Color at 140C EXAMPLE Melt 2 4 o 24 NO. TREATING AGENT Color Hrs. Hrs. Hrs. Hrs.

1 None 15 300 S00 2 Sodium p-tolucncsulfonchloramide I5 50 I00 125 500+ 3 N-Chlorosuccininiidc l5 5() 8t) 90 250 4 Ally chloride 15 35 50 no mo 5 X-Quinolinesul fnnyl chloride 15 25 30 35 8O 6 Acryloyl chloride l5 Z0 Z5 30 50 7 Mcso mudichlorng succinic acid I l0 15 2t) 25 (i0 8 p lolucnc'sullonyl chloride I5 30 35 40 9o 9 Funiaroyl.cliloridc 25 25 40 45 80 IO Bcnzyl chloride" I5 Z5 30 35 l l Benvoyl chloride" l5 l5 12 o-phthaloyl chloride" I l'5- 3U 9U TABLE 1- Continued "One drop added Thus, it can be seen that organic compounds containing a labile halogen, and mixtures of such compounds, impart outstanding color stabilization to refined maleic anhydride. Monocarboxylic acid halides such as benzoyl chloride and acryloyl chloride, as well as polycarboxylic acid halides such as fumaroyl chloride and phthaloyl chloride, demonstrate superior results as color stabilizing treating agents for refined maleic an- We claim:

1. A composition comprising a major amount of refined maleic anhydride and a color stabilizing amount of an organic compound containing a labile halogen.

2. A composition of claim 1 wherein the stabilizing amount comprises from about 0.01 to about I000 parts per million by weight of the refined maleic anhydride.

3. A composition of claim 1 wherein the stabilizing amount comprises from about 0.01 to about parts per million by weight of the refined maleic anhydride.

4. A composition of claim 1 wherein the organic compound is selected from the group consisting of mcso-a,a'dichlorosuccinic acid, benzyl chloride, benzal chloride, benzotrichloride, and mixtures thereof.

5. A composition of claim 1 wherein the organic compound containing the labile halogen comprises a monocarboxylic acid halide.

6. A composition of claim 5 wherein the monocarboxylic acid halide is selected from the group consisting of benzoyl chloride and acryloyl chloride.

7. A composition of claim 1 wherein the organic compound containing the labile halogen comprises a polycarboxylic acid halide.

8. A composition of claim 7 wherein the polycarboxylic acid halide is selected from the group consisting of fumaroyl chloride and phthaloyl chloride.

9. A method which comprises introducing into refined maleic anhydride a color stabilizing amount of an organic compound containing a labile halogen.

10. A method of claim 9 wherein the organic compound containing the labile halogen is selected from at least one of the group consisting of mew-madichlorosuccinic acid, benzyl chloride. benzal chloride, benzotrichloride, fumaroyl chloride, acryloyl chloride, benzoyl chloride and phthaloyl chloride. 

1. A COMPOUND COMPRISING A MAJOR AMOUNT OF REFINED MALERIC ANHYDRIDE AND A COLOR STABILIZING AMOUNT OF AN ORGANIC COMPOUND CONTAINING A LIBILE HALOGEN.
 2. A composition of claim 1 wherein the stabilizing amount comprises from about 0.01 to about 1000 parts per million by weight of the refined maleic anhydride.
 3. A composition of claim 1 wherein the stabilizing amount comprises from about 0.01 to about 100 parts per million by weight of the refined maleic anhydride.
 4. A composition of claim 1 wherein the organic compound is selected from the group consisting of meso- Alpha , Alpha ''dichlorosuccinic acid, benzyl chloride, benzal chloride, benzotrichloride, and mixtures thereof.
 5. A composition of claim 1 wherein the organic compound containing the labile halogen comprises a monocarboxylic acid halide.
 6. A composition of claim 5 wherein the monocarboxylic acid halide is selected from the group consisting of benzoyl chloride and acryloyl chloride.
 7. A composition of claim 1 wherein the organic compound containing the labile haloGen comprises a polycarboxylic acid halide.
 8. A composition of claim 7 wherein the polycarboxylic acid halide is selected from the group consisting of fumaroyl chloride and phthaloyl chloride.
 9. A method which comprises introducing into refined maleic anhydride a color stabilizing amount of an organic compound containing a labile halogen.
 10. A method of claim 9 wherein the organic compound containing the labile halogen is selected from at least one of the group consisting of meso- Alpha , Alpha ''-dichlorosuccinic acid, benzyl chloride, benzal chloride, benzotrichloride, fumaroyl chloride, acryloyl chloride, benzoyl chloride and phthaloyl chloride. 